The objective of Project I (Measurement) is to develop and evaluate instruments used to measure oracy and literacy in Spanish and English in English-language learners. We propose a five-year study of 1600 children in grades K-3 who are English-language learners. Primary data collection will occur in the first two years. In subsequent years, efforts will be devoted to hypothesis-oriented analyses of the first two years of data collection, and the analysis of measurement-related hypotheses based on data collected in Project II (Development) of this program project. A cross-sectional design is proposed over t he same age range studied longitudinally in Project II (Development). The data collection scheme in Project I (Measurement) will allow efficient development of new tests and initial estimation of item parameters and test properties using a pool of subjects that span the age and ability range of Project II, but requiring only one year of primary data collection. This approach of superimposing a cross-sectional design over a longitudinal design allows us to assess potential effects of repeat testing (so called practice effects) in the longitudinal study. More importantly, Project I will permit identification of appropriate basal and ceiling rules for all tests, allow reduction in administrative time for all tests, thoroughly evaluate the psychometric properties of all tests without comprising domain coverage, and test specific hypotheses about the inter-relationship of the various constructs in English-language learners. Three specific aims are proposed: 1) language proficiency addresses the psychometric properties and construct validity of tests used to measure oracy, literacy, and literacy-related skills in English and Spanish in English language learners; 2) literacy-related skills addresses the nature of the constructs that underlie development of language and literacy skills in English and Spanish, and their interrelationships; 3) psychometric characteristics provides for instrument development and refinement through systematic evaluations of the reliability and validity of measures of oracy and literacy used across the program project. Altogether, Project 1 is central to the goals of the research program, providing tools and a hypothesis-oriented evaluation of these tools essential to the Projects II-V. In addition, Project I highly responsive to the overall goals of the RFA, responding to the call for improve measurement strategies and normative development studies of English-language learners.